The present invention relates generally to permanent magnet structures and more particularly, to those structures which are utilized in electric machinery such as motors and generators.
As is well known in the art of electric machinery, the flux density of conventional permanent magnet structures is less than optimal due to various magnetic losses. The most common magnetic losses encountered with permanent magnet structures in electric machinery are due to flux leakage or unnecessary reluctance in the magnetic circuit thereof. When, traditional magnetic materials, such as Alnico, are utilized in these permanent magnet structures, adjacently disposed north and south poles can not be arranged on a cylindrical surface within the electric machinery without encountering flux leakage from corresponding north and south poles remotely located from that cylindrical surface. Although shunting rings can be incorporated to preclude such flux leakage in some electric machinery designs, they are very cumbersome to those designs. Pole pieces can be incorporated in those electric machinery designs where shunting rings are not possible but they only reduce such flux leakage and therefore, do not completely resolve the problem. Furthermore, as disclosed by M. Marinescu, et al in their paper entitled NEW RARE-EARTH PERMANENT MAGNET STRUCTURE FOR PRODUCING OPTIMAL MAGNETIC FIELDS IN MAGNETIC SEPARATION DEVICES, COMPARISON WITH PREVIOUS SYSTEMS; pages 163-181 of the Proceedings of the Ninth International Workshop on Rare-Earth Magnets and Their Applications, and Fifth International Symposium on Magnetic Anisotropy and Coercivity In Rare Earth-Transition Metal Alloys which were held from Aug. 31, 1987 through Sep. 3, 1987, arrangements of magnetized segments fabricated from magnetically rigid materials are also known which reduce such flux leakage but do not completely resolve the problem.